Terminal for electric switches



' ,1944. H; BRADLEY ETAL TERMINAL FOR ELECTRIC SWITCHES 2 Sheets-S het 1 Filed Oct. 24, 1941 I INVENTORS HARRY L. BRADLEY HANS PETERSEN v 0212; 1G

Feb. 22, 1944.

H. 1.. BRADLEY EI'ALf TERMINAL FOR ELECTRIC SWITCHES Filed Oct. 24, 1941 2 SheetsSheet 2 INVENTORS HARRYLBRADLEY HANS PETERSEN wwaxqw A'ITORNEY.

atented Feb. 22, E944 2,342,177 TERMINAL FUR ELECTRIC SWE'KCEES Barry L. Bradley, River Hills, and Hans Petersen, Wauwatosa, Wis., assig'nors to Allen-Bradley @ompany, Milwaukee, Wis, a corporation oi Wisconsin Application ()ctober 24, 1941, Serial No. 416,286

- 3 Claims.

This invention relates ingeneral to terminals for electric switches and in particular to terminals for the stationary contacts in an electric switch in which the stationary contacts and the complementary movable contact are Within an insulating enclosure.

A switch of the type wherein the stationary and movable contacts are within an insulating enclosure is shown and described in Patent No. 2,071,149 issued to G. O. Wilms, et al., and which patent is assigned to the Allen-Bradley Company, which company is also the assignee of this present application. Switches of this type have been successfully built in current carrying capacities of 25,50 and 100 amperes. The next higher capacity switch is rated at 150 amperes and much effort has been expended and many experiments have been carried on to build a switch of the type noted above in this capacity of 150 amperes. One of the chief problems encountered was the reduction of the high temperature in the current carrying parts of the switch. Also provision had to be' made in a stationary contact structure which would align itself with its complementary movable contact, which would remain in a fixed position after alignment, which would withstand heavy mechanical shock and which would transmit shock evenly and over a wide area to the insulation material in which itself is supported.

It is also highly desirable that the stationary contact structure be of a simple construction and be interchangeable with its other corresponding contact structure.

In the type of switch shown'in Patent No. 2,071,149 a movable contact bar is operable to bridge two stationary contacts. There are, therefore, two junctures in each pole of such a switch and these two junctures are enclosed within walls of insulating material which material is a poor conductor of heat. It is paramount, in the design of switches for the control of electrical power in the industrial field, that the switch be comparable to or smaller in size than existing available equipment. The size of the terminal is, therefore, limited.

Heretofore switches of this type of smaller capacities as 50 and 100 amperes employed a terminal of two separate parts thereby creating a juncture in each terminal. This juncture did not, however, cause trouble as the currents were of smaller values and the parts of the switch were large enough and were proportioned properly to carry off the generated heat.

It is significant that the heat in this type of switch is largely dissipated by conduction into the connecting power lines and load lines and little heat is dissipated by radiation. or by convection.

Our invention is the discovery that a one piece conductor having a flat shank, a base portion for the contact and having sumcient mass will provide a terminal and contact face of size in proportion to other parts of the switch and operate at a low temperature.

Also our invention is a. combination terminal and contact face wherein a one piece conductor with a mounting means of two brackets and bolt connection provides for strength against shock, even distribution of shock, alignment, rigidity after alignment, ease of replacement and nterchangeability.

. The practice or our invention is illustrated in the followin description, .the accompanying drawings being part thereof.

Figure l is a front view, part in section, of a switch mechanism incorporating our invention.

Figure 2 is a side view in section of the switch mechanism of Figure 1, taken along the lines 2-? in Figure 1.

Figure 3 is an enlarged perspective view of the terminal of our invention assembled with its supporting brackets and clamping screw, and

Figure 4 1s an enlarged perspective view of the component parts of the terminals, disassembled.

Referring to, Figures 1 and 2, the numeral t indicates the base plate to which is attached the insulating housing denoted generally b numeral E5 The insulating housing 5 is made up of back section 5, front section 7, three bottom sections t, and holding plate Q.

The section 6 and i, in assembled relationship as shown, are securely held to the back plate t by means of bolts it and nuts H, which bolts in turn are riveted to'bacl: plate t.

The housing 5 is completed by the three bottom sections 8 and holding plate 9, the latter being attached to back section it by means of threaded inserts and screws not shown.

The. switch mechanism in this instance is a three pole switch and the three chambers are formed by the walls of the cavities in back. section ii, front section l and the bottom sections 8.

Our invention apart from its corresponding enclosure is shown in Figures 3 and 4 and consists essentially in the form shown as a terminal concluctor, a bracket arrangement and a clamping screw which screw also serves as a means of connection to a conducting line connection.

The bracket arrangement consists of a bottom bracket 53, a top bracket M, which brackets are secured to the top wall of section 6 by means of bolts I5, lock washers 32 and nuts l6. As is shown in Figures 1 and 2, the bolts pass through holes in top wall of section 6. Terminal conductor i2 is secured to the face of bracket l3 by means of clamping screw H, which passes through clearance holes 23 and 22 of brackets l4 and 13 respectively.

Screw I! is threaded into conductor 12 at threaded hole 2| with lock washer 24 between head of screw H and corresponding face of bracket 14. As is shown the top wall of section 6 has rectangular openings therein indicated as at 33 and 34; in which are located the shank portions of conductor 12 and brackets l3 and 14.

As accessibility and replacement are of prime importance, the switch as described provides for replacement of terminal conductors l2 by removal of front section I and of the corresponding screw IT. The terminal conductor I2 is then dropped down and moved forwardly out of the front opening. To permit removal of a conductor 12 at the back of switch, opening 34 is formed with a tapered enlargement as indicated by dotted line in Figure 2.

It is to be noted that there is an offset indicated as 35 in the terminal conductor l2. As the terminal conductors are placed in the respective openings 33 and 34 with theirlike surfaces facing in opposite directions a clearance is afforded to allow accessibility in approach to screws l1 and nuts l8.

Clamping screw I! which is screwed into threaded hole 2| in terminal conductor I2 passes through clearance hole 22 in bottombracket I3 and through clearance elliptical opening 23 in top bracket [4. The clearance hole 22 is slightly over-size to allow for alignment of the stationary contact. The opening 23 is an oversize opening as regards diameter of clamping screw IT to allow for change in dimension of top wall of insulation material which may be expected.

Lugs of the power lines or supply lines are each connected to the corresponding face of terminal conductor 12 by means of nut l8 and lock washer I9.

Stationary contacts 25 consistingessentially of silver, are secured to the copper terminal conductor l2, and movable contacts 26, consisting essentially of silver, are secured to the copper contact bar 3|.

The contact bar 3| is positioned on a post 21 by means of a spring 28. The post 21 in turn is mounted on cross bar 29 which cross bar is actuated by an electro-magnetic or by manual means to engage or disengage the movable and stationary switch contacts.

In' one particular device each contact is held in the closed position by a force of six pounds or a force of twelve pounds is exerted by spring 28 normal to the engaging surfaces of the contacts. The cross bar 29 moves to the closed position with great rapidity and therefore, there is a great impact on the stationary contacts 25 which is transmitted to the top wall of insulation section 6.

The power lines are attached to the face of terminal conductor l2 and these power lines are of such size that considerable stress may result whenthe connection is made.

Our invention as embodied in the foregoing disclosure provides suiflcient area to the insulation to distribute impact-to a safe value per unit area and also distributes the stress, incident to connecting of power lines, to both surfaces of the insulation wall thereby reducing stress to a safe value per unit area. I

The fiat shank portion of terminal conductor l2 provides the requisite cross sectional area for conducting electric current and a large surface for the contact of power or load conductor.

At the end of each switch chamber is an arcing electrode 30 which is the subject matter of application, Serial No. 352,206 of Lynn H. Matthias filed August 1-2, 1940.

While in accordance with the patent statutes we have disclosed the foregoing details of a specific embodiment of our invention, and while certain of the claims are directed to the details of this prefered embodiment, it is to be understood that the principles disclosed are capable of much wider adaptation to the art of electric switches generally. We desire, therefore, that the language of our claims shall be accorded the broadest reasonable construction, and that our invention shall be limited only by What is expressly stated therein and by the prior art.

What we claim as our invention is:

1. An electric switch of the class described capable of carrying 150' amperes continuously comprising an enclosure of insulating material, a pair of stationary contacts within the chamber of said enclosure, a movable contact within the chamber adapted to bridge said stationary contacts and a conductor-for each stationary contact of integral mass having a flat base portion providing a face for the stationary contact and a shank portion substantially at right angles to said flat base portion and having a cross-section of fiat contour, and a bracket for each conductor having a part arranged between the conductor and the insulating material of the enclosure to distribute the shock into the insulating material of the movable contact on the engagement thereof with the stationary contact, and said shank portion of each conductor having sufiicient mass and capacity to absorb and transfer heat of the contacts at a rapid rate and having sufiicient area for attachment to the conductor to transfer said heat rapidly to the conductor.

2. An electric switch comprising. an enclosure of insulating material, a pair of stationary contacts within the chamber of said enclosure, a movable contact within the chamber adapted to bridge said stationary contacts and a pair of integral conductors each extending through a wall of said enclosure, each conductor forming a terminal on the outside of said enclosure and a base for one stationary contact on the inside of the chamber, and a bracket for each conductor having a part arranged between the conductor and the insulating material of the enclosure to distribute the shock into the insulating material of the movable contact on the engagement thereof with the stationary contact, said bracket having means for its attachment to the wall of the enclosure and provided with a support means for the conductor at its terminal portion.

3. An electric switch comprising an enclosure of insulating material, a pair of stationary contacts within the chamber of said enclosure, a movable contact within the chamber adapted to bridge said stationary contacts and a pair of conductors of integral mass each extending through a wall of said enclosure; each said conductor having a flat base portion providing a face for the stationary contact and a shank portion substantially at right angles to said base portion having a cross section of fiat contour to afford a fiat surface for connection to a complementary line connection, and a bracket for each conductor havin a part arranged between the conductor and the insulating material of the enclosure to distribute provided with a support means for the conductor 'at its terminal portion and said conductor of said proportions to transmit heat from the contacts to the terminal for transmission into the 5 complementary line connection.

HARRY L. BRADLEY. HANS PETERSEN. 

